Dehydrogenation catalyst and process



United States Patent Archibald P. Stuart, Media, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporanon of New Jersey No Drawing. Application May 28, 1952,

Serial No. 290,570

v a Claims. or. 260-668) This invention relates to new catalytic compositions. More particularly, the invention relates to new dehydrogenation catalysts and processes for their use.

Various metals and metallic oxides, either alone or deposited on a carrier, have heretofore been employed in dehydrogenation processes. Such catalysts and catalytic' compositions, however, are usually subject to one or more difiiculties which limit their use in commercial operations. For example, such catalysts are expensive to prepare, orare not sufficiently effective to cause dehydrogenation or naphthenes without the use of relatively drastic conditions, and the use of drastic conditions causes undesired reactions such as cracking. Also, heretofore described catalysts are often rapidly deactivated in the dehydrogenation reactions.

An object of the present invention is to provide a highly effective, inexpensive dehydrogenation catalyst.-

A further object is to provide a catalyst which may be employed for long periods of time without deactivation. Anotherobject is to provide a catalyst effective in dehyd'rogenation reactions wherein only relatively mild COD: ditions are required. A still further object is to provide a process for reforming hydrocarbons, and especially for dehydrogenating and isomerizing hydrocarbons. I

It has now been found that by incorporating a small amount of a nitrogen-containing organic base on a dehydrogenation catalyst comprising a metallic oxide deposited on a'carrier there is produced a catalytic composition remarkably effective in dehydrogenation processes, and which is also effective for other reforming reactions, such as isomerization. catalytic composition is inexpensive, has a long life, and is efiective for the dehydrogenation and isomerization of hydrocarbons under relatively mild conditions.

In my co-pending patent application Serial No. 208,232,

filed January 27, 1951, there is described and claimed a catalytic composition comprising a metal sulfide deposited on a carrier and a chemisorbed quantity of an organic nitrogenous base. This catalytic composition is employed in hydrogenating reactions, and is to be distinguished from the catalytic composition of the present invention,

which comprises a metallic oxide deposited on a carrier and a chemisorbed quantity of an organic nitrogenous base, and which is used in reforming processes such as the dehydrogenation of naphthenes.

In accordance with the present invention, a metallic oxide is deposited on a carrier and the resulting composition is treated with an organic nitrogenous base. The effective quantity of the base is that amount which is chemisorbed by the metallic oxide-carrier composition, and the so-formed composition containing chemisorbed organic nitrogenous base is the catalyst of the present invention.

By the expression chemisorbed quantity, and terms of similar import, as used herein, is meant that quantity of organic nitrogenous base adsorbed on the metallic oxide-carrier composition which is held by bonds stronger It has been further found that this 2,742,515 Patented Apr. 17, 1956 than mere physical adsorption. Thus, physically adsorbed base may be relatively readily removed by desorption, whereas the chemisorbedbase can be removed only by resort to relatively drastic conditions. For example, the portion of organic base held by physical adsorption is readily removed by maintaining the composition at a temperature above the boiling point and below the decomposition point of thebase in a stream of an inert gas for time sufficient to achievedesorptionffrom about 1 to 6 hours usually being sufficient. The chemisorbed portion of the organic" base is not affected by this operation.

vMetallic oxide components which may be employed in the present catalytic composition are preferably the oxides of the metals of group 6 of the periodic table. Preferred metallic oxidesto employ are the oxides of chromium, molybdenum and tungsten. Other metallic oxides, such as the oxides of copper, zinc, and vanadium, may be employed with good results as hereinafter de-' scribed. These metallic oxides may be deposited on carriers heretofore employed, including, for example, bauxite, alumina, silica gel, mixtures of alumina andsilica gel,

' including physical mixtures and coprecipitated compositions, and the like. I Alumina is the preferred carrier to employ with the preferred metal oxides and may be employed with other metal oxides if desired. However, with basic or amphoteric metallic oxides, such as the oxides of zinc or copper, it is preferred to employ an acid type carrier, preferably a siliceous carrier, i. e., a carrier having silica as a component thereof. A preferred embodiment of the present invention comprises'using as the carrier aspent cracking catalyst. In patent application Serial No. 200,700, filed December 13, 1950, now Pat ent No." 2,635,081, there is described and claimed a catalytic composition including as a component a spent cracking catalyst, and the spent cracking catalyst asthere described is advantageously employed as the carrier in the present catalytic compositions. The spent cracking catalyst is preferably a catalyst consisting of silica and alumina which has been employed for the catalytic cracking of hydrocarbons until. the cracking activity in the cracking operation has decreased at least about 30% below its initial value, so that regeneration for further use in cracking is not feasible. Silica-alumina cracking catalysts are well'known, and generally contain a ratio of silica to alumina of 1:1 to15 :1 and preferably from to silica, from 30% to 10% alumina, and not more than 10% of other materials.

The quantity of metallic oxide deposited on a carrier 'may be varied from about 2% to'20% by weight of the carrier, but preferably is maintained wtihin the range of from 5% to 15% by weight.

The I organic nitrogenous bases which may be employed are the organic nitrogen-containing compounds having a basic reaction, or a nitrogen-containing compound which is converted thereto under the conditions of the hydrogenation processes such as butyl cyanide and cyclohexanone oxime. It is preferred to employ an or-. ganic base wherein a'nitrogen atom is connected in a ring which may be of aromatic or naphthenic character. Ex! amples of preferred organic bases are quinoline, pyridine, quinaldine, piperidine, pyrrole, and their alkyl derivatives. Other organic nitrogenous bases which may be employed with good results include, for example, aniline, toluidine, decylamine, and other amines. The nitrogen base should not be decomposed under dehydrogenating conditions, and hence bases wherein the nitrogen atom ,is connected to a tertiary carbon atom are not preferred. Preferred nitrogenous bases are those wherein the nitrogen atom is connected to a primary or secondary carbon atom or atoms, and which have from 4 to 16 arbon atoms per molecule.

to those skilled in the art. For example, the present catalytic composition is advantageously employed for the dehydrogenation of substantially pure naphthenes, such as cyclohexane, methylcyclohexane, or dimethylcyclohexane to prepare, respectively, benzene, toluene, or xylene. Mixtures of naphthenes may also be employed, such as mixture of cyclopentanes and cyclohexanes, the cyclopentanes being isomerized to cyclohexanes in the process, and subsequently dehydrogenated to the corresponding aromatic. Also,-when other metallic oxides, carriers or organic nitrogenous bases are employed, as hereinbefore described, substantially similar results are obtained as described in the above example.

The invention claimed is:

1. Process for the dehydrogenation of hydrocarbons boiling in the gasoline range which comprises contacting said hydrocarbons under dehydrogenating conditions with a catalytic composition comprising a carrier selected from the group consisting of bauxite, alumina, silica gel, mixtures of alumina and silica gel, and a spent cracking catalyst having deposited thereon from 2% to of a metallic oxide dehydrogenating catalyst selected from the group consisting of chromium oxide, molybdenum oxide, tungsten oxide, copper oxide, zinc oxide and vanadium oxide and having chemisorbed thereon, in an amount effective to increase dehydrogenating activity, an organic nitrogenous base having from 4 to 16 carbon atoms per molecule.

2. Process according to claim 1 wherein said metallic oxide is molybdic oxide.

3.Process according to claim 1 wherein said organic nitrogenous base is quinoline.

4. Process for the dehydrogenation of naphthenes which comprises contacting said naphthenes under dehydrogenating conditions with a catalytic composition consisting essentially of alumina having deposited thereon from 2% to 20% molybdic oxide and having chemisorbed thereon from 0.01 to 0.2 milliequivalents of quinoline per gram of molybdenum oxide-alumina catalyst.

5. Process for the preparation of an improved dehydrogenating catalytic composition which comprises depositing from 2% to 20% of a metallic oxide selected from the group consisting of chromium oxide, molybdenum oxide, tungsten oxide, .copper oxide, zinc oxide and vanadium oxide on a carrier selected from the group consisting of bauxite, alumina, silica gel, mixtures of alumina and silica gel, and a spent cracking catalyst and treating the resulting composition with an organic nitrogenous base having from 4 to 16 carbon atoms per molecule whereby the final composition has a chemisorbed quantity of said base.

6. Process for the preparation of an improved dehydrogenating catalytic composition which comprises depositing molybdenum oxide on alumina and treating the resulting composition with quinoline in the vapor phase to obtain a. chemisorbed quantity of from 0.01 to 0.2 milliequivalents of said base per gram of molybdenum oxide-alumina composition.

7. An improved dehydrogenating catalytic composition comprising a carrier selected from the group consisting of bauxite, alumina, silica gel, mixtures of alumina and silica gel, and spent cracking catalyst, having deposited thereon from 2% to 20% of a metallic oxide selected from the group consisting of chromium oxide, molybdenum oxide, tungsten oxide, copper oxide, zinc oxide and vanadium oxide, and having a chemisorbed quantity, effective to increase dehydrogenating activity, of an organic nitrogenous base having from 4 to 16 carbon atoms per molecule. 1

8. An improved dehydrogenating catalytic composition according to claim 7 wherein said organic nitrogenous base is from 0.01 to 0.2 milliquivalent per gram of the carrier-metal oxide composition.

References Cited in the file of this patent 7 UNITED STATES PATENTS Rittmeister Feb. 4, 1936 2,029,895 2,162,276 Weiss June 13, 1939 2,184,235 Groll et al. Dec. 19. 1939 2,322,622 Fischer et'al. "June 22, 1943 2,369,524 Berg et a1 Feb. 13, 1945 7 2,375,573 Meier May 8, 1945 2,409,695 Laughlin Oct. 22, 1946 2,430,632 Fetterly Nov. 11, 1947 2,454,724 Tamele et al. Nov. 23, 1948 OTHER REFERENCES Mills et al. (publication): Journal of the American Chemical Society, vol. 72, issue 4, pages 1554-1560, April 1950. 

1. PROCESS FOR THE DEHYDROGENATION OF HYDROCARBONS BOILING IN THE GASOLINE RANGE WHICH COMPRISES CONTACTING SAID HYDROCARBONS UNDER HYDROGENATING CONDITIONS WITH A CATALYTIC COMPOSITION COMPRISING A CARRIER SELECTED FROM THE GROUP CONSISTING OF BAUXITE, ALUMINA, SILICA GEL, MIXTURES OF ALUMINA AND SILICA GEL, AND A SPENT CRACKING CATALYST HAVING DEPOSITED THEREON FROM 2% TO 20% OF A METALLIC OXIDE, DEHYDROGENATING CATALYST SELECTED FROM THE GROUP CONSISTING OF CHROMIUM OXIDE, MOLYBDENUM OXIDE, TUNGSTEN OXIDE, COPPER OXIDE, ZINC OXIDE AND VANADIUM OXIDE AND HAVING CHEMISORBED THEREON, IN AN AMOUNT EFFECTIVE TO INCREASE DEHYDROGENATING ACTIVITY, AN ORGANIC NITROGENOUS BASE HAVING FROM 4 TO 16 CARBON ATOMS PER MOLECULE. 